Try 9 overline ")4125"this just produces the equation not the solution

If you want the full solution expanded out then include that formula by insert/object/formula in a Writer (text) document on the appropriate lineyou will have to use ordinary lines around it with appropriate spaces inserted to align the remaining elements of the sum

This advice comes from an earlier post but seemed relevant to add here.

Last time I played with this, I found it simpler to skip OO Math and just stick to plain text. It's still a pain to manage but at least you don't have to fight with OO Math. Using "digit space" characters (U+2007) may help but some fonts may still not allow good alignment.